SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2ad6a51fca52bba618788d2c53e88cfede5bef5740970794e2a481a6093972c2' 
  AND token = 'XUQuXRaCSwGK7LghUfJ+N7YtUz5MF4GjpD80HqwQXDQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00059

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}